For multiple reasons, farmers are seeking biologically-based pest control alternatives to commercial synthetic chemical pesticides. One “biocontrol” strategy is to increase the presence of the insects' natural enemies in the environment in which the crops are grown. These natural enemies may include beneficial entomopathogenic nematodes such as Steinernema spp or Heterorhabditis spp. These beneficial nematodes are parasites that prey on a variety of damaging insects but pose no danger to plants or humans.
Commercial production of beneficial nematodes can be in vitro (e.g., in fermentation tanks), or in vivo using susceptible insect hosts. Although both production systems have advantages, in vivo systems generally result in the production of better quality and more virulent nematodes. Further, more nematode species can be produced in vivo and in vivo production methods do not require the use of expensive and complex equipment.
However, in vivo production of beneficial nematodes requires the large scale production of an insect host that can be infected with the nematodes. Infection of a host insect allows the nematodes to multiply within the host's cadaver. After the hosts are infected and the nematodes begin to multiply, the infected cadavers are applied to the crop environment. Distributing the nematodes along with a food supply (i.e. the infected cadavers) increases the nematodes' survivability while the nematodes forage for damaging insects in their new crop environment.
Mealworm larvae (Tenebrio molitor) are ideal hosts for the nematodes. Mealworm larvae are relatively easy to mass produce, readily susceptible to infection by many nematode species, and the infected mealworm larvae cadavers are resilient enough to be manipulated without breakage or disintegration.
Mass production of the mealworm larvae involves mixing the larvae into a food aggregate where the larvae can grow and mature. However, the larvae develop at different rates so that there is always a range of larvae sizes in any mealworm aggregate mix. Removing the larvae from the food aggregate and separating out the optimal-sized larvae is a dirty and time-consuming process. In the past, workers have used progressively smaller manual sifters to hand-filter the aggregate mix and thereby separate out the larvae. However, in addition to being labor intensive, the sifting process results in dust and frass that becomes airborne. The resulting airborne particulate materials contaminate workers' immediate environment and potentially pose dangers to the workers' health.
The need exists for a quick, efficient, and automated system for separating optimally-sized mealworm larvae from an aggregate mix so that the nematode production process can proceed expeditiously. The current invention comprises a modular insect separator system and an associated process for moving relatively large volumes of aggregate mix through the system.
The preferred embodiment of the current system has the capacity to process up to 1,000,000 mealworm larvae per hour. The system separates the aggregate mix into: (1) mealworm larvae larger than 90 mg; (2) mealworm larvae between 70 mg and 90 mg; (3) unconsumed food materials and larvae smaller than 70 mg, and (4) insect frass.
While the preferred embodiment of the current invention is directed to the production of mealworm larvae for bio pest control purposes, the production and separation of other types of insects should be considered to be within the scope of the invention.